hairline
hair.line \-.li-n\ n 1: a very slender line : as 1a: a tiny line or crack on a surface 1b: a fine line connecting thicker strokes in a printed letter 2a: a textile design consisting of lengthwise or crosswise lines usu. one t hread wide 2b: a fabric with such a design 3: the outline of the scalp or of the hair on the head - hairline aj